Originally Posted by PhysicsMan
At one instant in time, imagine two skiers of equal weight going at the same speed at the apices of their respective carved turns. Imagine they are both doing 180 degree, traverse-to-traverse, perfectly carved, razor thin, RR-track turns.
The better skier (#1) is executing a shorter radius (ie, higher-G) turn, with their skis far to the outside, and is actively extending at this point in preparation for a retraction-based cross-under transition which will occur a second or two later. The less skilled skier (#2) is executing a larger radius, lower-G turn, and /or may even be starting to sink in preparation for a later "up and over" extension-based transition. Skier #2 may even be settling back on his tails a bit at the apex because he is getting a bit defensive.
Consider the force each of them is exerting on the snow in a direction perpendicular to their edged bases (ie, the "normal" force) at the apices of each of their turns. Skier #1 is exerting considerably more force in this direction (ie, into the snow) both because of the higher-G of his/her turn, as well as because of the phase he/she is at in his management of pressure (ie, extending). Skier #2 exerts less normal force into the snow at the apex of his turn because of the assumed lower-G of his turn, as well as because he is removing some pressure from his skis because he is either doing nothing or starting to flex instead of extending at this point in his turn.
For most snow friction mechanisms (e.g., snow compaction, snow displacement, hydrodynamic base drag, etc.) the frictional force is almost perfectly proportional to the normal force that the ski exerts on the snow. Thus, compared to skier #2, skier #1 will be experiencing much more speed controlling friction when he/she is at the apex of his/her turn and his/her skis are pointed straight down the fall line. This frictional force on his/her skis is pointed uphill, directly opposite and subtracting from the down-slope component of gravity, and is occurring exactly when most needed.
I think this explains SSH's observation that Nolo and Uncle Louie don't seem to be gaining speed even when they are in the fall line. Actually, they probably *are* gaining speed, just not as much as SSH expects based on his own experience.
Next, consider what happens a second or two later to the two skers, when each is at the transition into the next turn. At this point, both are at opposite phases of their respective pressure management cycles. Skier #1 (using retraction / cross-under) will be flexing and exerting relatively less normal force on the snow. This has two major consequences. First, it allows him/her to carry as much across-the-hill speed as possible into the next turn, a good thing to ensure yet another high-G turn. Secondly, being light on the snow (ie, low friction) at this point in his turn doesn't mean that skier #1 will pick up additional speed because he/she is pointed (by assumption) directly across the hill and is, at least for the moment, effectively immune from gravity-induced acceleration.
Skier #2, OTOH, will be experiencing the most friction at this point in his turns (a.k.a., a heavy "bottom" to his turns). Yes, it will cause him/her to scrub off speed, but all this really does is make his entry into the next turn more difficult (ie, approaching stalling), and contribute towards much more exaggerated fast-slow swings in his velocity. Skier #1 maintains a much more consistent velocity over his/her entire turn cycle.
Tom / PM
You are freakin' brilliant!
You have, in a very scientific way that I can actually visualize and understand, described exactly what was going on and the difference that I observed. Furthermore, this is exactly what Uncle Louie and VSP observed and helped me begin to remedy.
Interestingly for me, skier #2 will compound his psychological problem as the accelleration increases his speed from turn to turn, since his speed will increase to the point of bail-out (sounds familiar to me!). I am humbled by and grateful for both your insight and your ability to communicate it, my friend. Thank you!